Chemistry. TOPIC : Redox Reactions. products are PH3 and NaH2PO2. This reaction is an examplee of. (b) Reduction (d) Neutralization

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1 TOPIC : Redox Reactions Date : Marks : 1 mks Time : ½ hr 1. When P reacts with caustic soda, the products are PH and NaHPO. This reaction is an examplee of (a) Oxidation (c) Oxidation and reduction (redox) (b) Reduction Neutralization. Following reaction describes the rusting of iron is incorrect + (a) This is an example of a redox reaction (b) Metallic iron is reduced to Fe + (c) Fe is an oxidising agent Metallic iron is a reducing agent. Oxidation involves (a) Loss of electrons (c) Increase in the valency of negative part (b) Gain of electrons Decrease in the valency of positive part. Which of the following is the most powerful oxidizing agent (a) F (b) Cl (c) Br I 5. Strongest reducing agent is (a) F (b) Cl (c) Br I 6. Which of the following acid possesses oxidising, reducing and complex forming properties (a) HNO (b) H SO (c) HCl HNO 7. In the conversion Br BrO, the oxidation state of bromine changes from (a) 1 to 1 (b) to 1 (c) to + 5 to 5 8. Oxidation number of nickel in Ni(COO (a) (b) + (c) + 9. The oxidation number of carbon in (a) (b) + (c) + 1. The oxidation number of Cr in KCrO 7 is (a) +6 (b) 7 (c) The brown ring complex compound is formulated as [ Fe ( H O) 5 NO] SO. The oxidation state of iron is (a) 1 (b) (c) 1. The oxidation number of phosphorus in Ba ( H PO ) is (a) 1 (b) + 1 (c) + + ) CH O is + Fe + O Fe + 6 Which one of O the following statement Page 1 of 6

2 1. The oxidation number of fluorine in (a) 1 (b) + 1 (c) + 1. Oxidation state of Fe in Fe O is (a) (b) 5 (c) 5 8 F O is 15. For the redox reaction MnO C O + H Mn + CO + H O the balanced reaction are MnO (a) 5 16 (b) (c) 5 16 C O + H the correct coefficients of the reactants for 16. One mole of N H loses 1 mol of electrons to form a new compound Y. Assuming that all nitrogen appear in the new compound, what is the oxidation state of N in Y? (There is no change in the oxidation state of hydrogen) (a) + (b) (c) The oxidation number of sulphur in (a), +1 and (b) +, +1 and (c), + 1 and +, + 1 and 18. Which of the following reactions involves oxidation-reduction (a) NaBr + HCl NaCl + HBr (b) HBr + AgNO AgBr + HNO (c) H + Br HBr 19. The oxidation number of sulphur in (a) (b) + (c) +. Which of the following is a redox reaction (a) NaCl + KNO NaNO + KCl (b) CaC O + HCl CaCl + H CO (c) Mg( OH) + NH Cl MgCl + NH OH Zn + AgCN Ag + Zn( CN ) 1. Oxygen has oxidation states of + in the (a) H O (b) CO (c) H O OF. When KMnO is reduced with oxalic acid in acidic solution, the oxidation number of Mn changes from (a) 7 to (b) 6 to (c) 7 to to. In which of the following compounds iron has lowest oxidation state (a) FeSO.( NH ) SO. 6H O (b) K Fe(CN ) 6 (c) Fe (CO) 5 Fe O (e) K FeO. Oxidation state of oxygen in hydrogen peroxide is (a) 1 (b) + 1 (c) 5. The oxidation number and the electronic configuration of sulphur in HSO is 6 (a) + ; 1s s p s (b) S 8,, S F H S respectively, are H S is NaOH + H SO NaSO + H O 6 + ; 1s s p s p Page of 6

3 6 1 (c) + ; 1s s p s p + 6; 1s s p 6 6. Oxidation states of the metal in the minerals haematite and magnetite, respectively, are: (a) II, III in haematite and III in magnetite (b) II, III heamatite and II in magnetite (b) II in haematite and II, III in magnetite III in haematite and II, III in magnetite 7. Which is the best description of the behaviour of bromine in the reaction given below H O + Br HOBr + HBr (a) Oxidised only (b) Reduced only (c) Proton acceptor only Both oxidised and reduced 8. The compound that can work both as oxidising and reducing agent is (a) KMnO (b) H O (c) BaO K CrO7 9. Which of the following substances acts as an oxidising as well as a reducing agent (a) Na O (b) SnCl (c) Na O NaNO. When copper turnings are added to because, copper (a) Displaces silver from the solution + (c) Is oxidised to Cu silver nitrate solution, a blue coloured solution is formed after some time. It is (b) Forms a blue coloured complex with AgNO + Is reduced to Cu P a g e

4 ANSWERS 1. (c). (b). (a). 11. (a) 1. (b) 1. (a) (c). (c).. (ac) (a) (c) 8. (a) 9. (c) 1. (a) 15. (a) 16. (a) 17. (c) 18. (c) 19. (b). (a) (b) 9. Solutions 1. (c) +. (b) The metallic iron is oxidised to Fe... (a) It is the process in which electrons are lost (de-electronation).. (a) Fluorine is a most powerful oxidizing agent because it consist of E o = +. 5 volt. 5. I act as a more reducing agentt than other ions. 6. HNO (Nitrous acid) acid acts as a oxidising, reducing agent and has complex formation properties. 7. (c) Br + 5 BrO, in this reaction oxidation state change from to (a) If any central metal atom combined with corbonyl group than central metal atom shows always zero oxidation state. 9. (c) 1. (a) CH O x + = x =. K CrO7 + x 7 = ; x 1 + = 1 x = 1 ; x = = (a) [ Fe ( H O) 5 NO] SO. 1 ; (b) Ba( H PO ) ; BaH P O + + x 8 = ; x = x = = (a) Fluorine always shows 1 oxidation state in oxides. 1. F e O x + ( 8) = ; x 8 = x = 8 ; 8 x = (a) MnO + 8H + 5e + Mn + C O CO + e 5 MnO + 5CO + 16 H Mn + H O + n + 1 CO + 8H O Page of 6

5 16. (a) 17. Thus the coefficient of MnO, C O Molecular weight 7! ""! 6 n = 5 n = Hence = Equivalent weight of Iodine. + andh in the above balanced equation respectively are, 5, 16. Oxidation 18. (c) H + Br H Br + Reduction 19. (b) Let the oxidation number of N in NaNO be x x + (-) = 1 + x = ; x = Zn+ AgCN Ag+ Znn (CN ). Reduction Oxidation 1. Oxygen have + oxidation state in OF. COOH + 7. (c) 5 + KMnO + H SO COOH + KSO + MnSO + 1CO + 8 H O In this reaction oxidation state of Mn change from + 7 to +.. (c) Iron has zero oxidation state in carbonyl complexes.. (a) In all peroxide oxygen shows 1 oxidation state. 5. H SO ( + 1) + x + ( ) = + + x 8 = ; x = 8 = + 6 Electronic configuration of sulphur in H SO is 6 s, s,. 1 p 6. In daematite (FeO), Fe is present (III) oxidation state and in magnetite (FeO) Fe is present in (II) and (III) oxidation state. 7. H O + Br HOBr + HBr In the above reaction the oxidation number of Br increases from zero (in Br ) to +1 (in HOBr ) and decrease from zero ( Br ) to 1 (in HBr ). Thus Br is oxidised as well as reduced & hence it is a redox reaction. 8. (b) Hydrogen peroxide ( H O) act as a both oxidising and reducing agent. 9. NaNO (Sodium nitrite) act both as oxidising as well as reducing agent because in it N atom is in + oxidation state (intermediate oxidation state) Oxidising property 5 P a g e

6 NaNO + KI + H SO Na SO + KSO + NO + H O + I Reducing property H O + NaNO NaNO + Reduction H O.. (c) Cu is above of Ag in electrochemical series and thus + + Cu + Ag Cu + Ag reaction occurs. Page 6 of 6